Water purifying system and backwash module control method thereof

ABSTRACT

Disclosed herein is a water purifying system, including: a raw water tank configured to store raw water; a filter unit configured to include a plurality of filtration modules for purifying the raw water and a plurality of valves for feeding or cutting off the raw water; a raw water pump configured to feed the raw water from the raw water tank to the filter unit; and a backwash module configured to feed backwash water to the filter unit, in which some of permeate water permeated by the filter unit is fed to the backwash module to be used as the backwash water and a feed pressure of the backwash water is fed by the raw water pump.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/298,835, filed on Oct. 20, 2016, which claims benefit of priority toKorean Patent Application No. 10-2015-0146906 filed on Oct. 21, 2015 inthe Korean Intellectual Property Office, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

Exemplary embodiments of the present invention relate to a waterpurifying system and a backwash module control method thereof, and moreparticularly, to a water purifying system and a backwash module controlthereof capable of performing backwash of a filter module using apressure of a pressure of produced water for membrane filtration withouta backwash pump.

Description of the Related Art

Recently, underground water, rivers, or the like are seriouslycontaminated due to heavy metal, pathogenic microorganism, micro organictoxic materials, or the like, and therefore safety guarantee of drinkingwater has been considered very important. Accordingly, an interest inresearches for a water purifying apparatus and a water purifying methodof drinking water to guarantee safe drinking water has been increased.As a typical water purifying method, there are a chlorination method, anozone treatment method, a membrane filtration method, etc. Here, a waterpurifying system for changing some of the treatment methods or operatingat least two treatment methods by step has been mainly used.

However, the existing chlorination method has a problem in thattrihalomethane is generated as a byproduct at the time of chlorinedisinfection and the existing ozone treatment method has a problem inthat ozone selectively treats organic toxic materials.

The water purifying method using the membrane filtration is a method forfiltering and removing pollutants included in raw water using a membraneas described in Korean Patent Laid-Open Publication No. 2003-0079479 andhas an advantage of reducing a scale of water purifying apparatus.However, there is a disadvantage in that a closure of the filtrationmembrane due to pollutants causes a frequent replacement of thefiltration membrane to incur excessive operation costs.

To solve the disadvantage of the water purifying method using themembrane filtration method, a separate backwash water storage tank andpump and a backwash system for backwash of the filtration membrane needto be constructed.

However, there is a problem in that the existing backwash system costs alot upon construction and incurs additional operation costs due to theoperation of the pump.

RELATED ART DOCUMENT Patent Document

(Patent Document 1) Korean Patent Laid Open Publication No. 2003-0079479(Published on Oct. 10, 2003)

SUMMARY OF THE INVENTION

An object of the present invention is to provide a water purifyingsystem and a backwash module control method thereof capable ofperforming backwash of a filter module using a pressure of producedwater for membrane filtration without a backwash pump.

Other objects and advantages of the present invention can be understoodby the following description, and become apparent with reference to theembodiments of the present invention. Also, it is obvious to thoseskilled in the art to which the present invention pertains that theobjects and advantages of the present invention can be realized by themeans as claimed and combinations thereof.

In accordance with one aspect of the present invention, there isprovided a water purifying system, including: a raw water tankconfigured to store raw water; a filter unit configured to include aplurality of filtration modules for purifying the raw water and aplurality of valves for feeding or cutting off the raw water; a rawwater pump configured to feed the raw water from the raw water tank tothe filter unit; and a backwash module configured to feed backwash waterto the filter unit, in which some of permeate water permeated by thefilter unit is fed to the backwash module to be used as the backwashwater and a feed pressure of the backwash water is fed by the raw waterpump.

The backwash module may be provided with two inlets and outlets.

The one inlet may be provided with a first valve for controlling a fluxof the raw water, the other inlet may be provided with a fourth valvefor feeding the permeate water, the one outlet may be provided with asecond valve for discharging the raw water, and the other outlet may beprovided with a third valve for discharging the backwash water.

The backwash module may be a pressure vessel or a pressure tank.

An inside of the pressure vessel may be provided with a piston movingalong a length direction, the piston may move to the first valve whenthe permeate water is fed to discharge the raw water to an outside ofthe pressure vessel and move to the third valve when the raw water isfed to discharge the backwash water to the outside of the pressurevessel.

An inside of the pressure tank may be provided with a diaphragm, thediaphragm may move to the first valve when the permeate water is fed todischarge the raw water to the outside of the pressure vessel and moveto the third valve when the raw water is fed to discharge the backwashwater to the outside of the pressure vessel.

The pressure tank may be installed at a movement limit position of thediaphragm and may further include a pair of plates provided with aplurality of through holes.

The inside of the pressure tank may include a balloon-like diaphragm,the diaphragm may be pressurized when the raw water is fed to dischargethe backwash water therein to the outside of the pressure tank andinflated when the permeate water is fed to discharge the raw water atthe outside thereof to the outside of the pressure tank.

The water purifying system may further include: a dirty water tankconfigured to discharge the backwash water after the backwash of thefiltration module.

An amount of permeate water of the filtration module may be increased asa required amount of the backwash water.

When the permeate water permeated by the filtration module is fed to areverse osmosis system, the flux of the raw water may be increased asthe required amount of the backwash water.

The water purifying system may further include: a flow meter configuredto be installed at a front end of the first valve to detect the flux ofthe raw water.

The first valve may be a flow control valve and the second to fourthvalves may be an on/off valve.

When the backwash module is fed with the permeate water, the first andthird valves may be closed and the second and fourth valves may be open,when the backwash is performed, the first and third valves may be openand the second and fourth valves may be closed.

The first valve may control the flux of the raw water depending on apreset backwash flux.

In accordance with another aspect of the present invention, there isprovided a backwash module control method of the water purifying systemhaving the configuration, in which the first to fourth valves arecontrolled depending on the re-feed of the permeate water to thebackwash module upon the backwash when the permeate water is fed to thebackwash module.

When the permeate water is fed and re-fed to the backwash module, thefirst and third valves may be closed and the second and fourth valvesmay be open.

When the backwash is performed, the first and third valves may be openand the second and fourth valves may be closed.

The first valve may control the flux of the raw water depending on thedetection result of the flow meter detecting the flux of the raw water.

The first valve may control the flux of the raw water depending on apreset backwash flux.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram schematically illustrating a water purifying systemaccording to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a first embodiment of a backwash moduleaccording to the water purifying system of FIG. 1;

FIG. 3 is a schematic diagram of a second embodiment of the backwashmodule according to the water purifying system of FIG. 1;

FIGS. 4 and 5 are schematic diagrams of a third embodiment of thebackwash module according to the water purifying system of FIG. 1; and

FIGS. 6 and 7 are schematic diagrams of a fourth embodiment of thebackwash module according to the water purifying system of FIG. 1.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, a water purifying system and a backwash module controlmethod thereof according to an embodiment of the present invention willbe described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram schematically illustrating a water purifying systemaccording to an embodiment of the present invention.

As illustrated in FIG. 1, the water purifying system according to theembodiment of the present invention is a system based on a filtrationmembrane method and includes a raw water tank 100 configured to feed rawwater, a raw water pump 200 configured to feed the raw water, a filterunit configured to purify the raw water, and a backwash module 400configured to wash a filter unit. The water purifying system includes aplurality of control valves or an on/off valve to open and close achannel for feeding and cutting off the raw water, feeding and cuttingoff backwash water, discharging permeate water permeated by a filterunit, or the like. In particular, the backwash module 400 is providedwith two inlets and outlets, in which each inlet and outlet are providedwith first to fourth valves 500.

The respective components of the present invention are connected to eachother by a transfer tube through which any one of the raw water, thebackwash water, and the permeate water is transferred. Unless separatelymentioned, it will to be understood that water circulating within thewater purifying system of the present invention is transferred along thetransfer tube.

The raw water tank 100 is used to temporarily store the raw water, inwhich the raw water is transferred to the filter unit by the raw waterpump 200.

The filter unit is configured to include a plurality of filtrationmodules 300 and a plurality of valves (these are illustrated in thedrawings but have no reference numeral) for feeding and discharging theraw water and the backwash water, in which the filtration module 300 maybe implemented as a microfiltration (MF) module, an ultrafiltration (UF)module, etc.

The microfiltration membrane is one of the polymeric separator membranesand has a micro pore of about 0.01 to 10 micros and stops suspensoid,colloidal particles, bacteria, or the like. The ultrafiltration membranepasses though water but does not pass through polymer material orcolloidal materials.

One filtration module 300 is configured by modularizing 10 to 100filtration membranes depending on raw water processing capacity. If anoperating time of the filtration module 300 is long, foreign materialsare attached to a surface of the filtration membrane, and thereforefiltration efficiency is reduced. As a result, it is essential to washthe filtration module 300. As the typical method for washing afiltration membrane, a method for separating pollutants attached to aseparator membrane by feeding washing water in a direction opposite to adirection in which the raw water is fed, without separately separatingand washing the filtration membrane is used. The method is defined asbackwash.

The permeate water purified by the filtration module 300 may betransferred to a separate permeate water storage tank and stored thereinor may be fed to a reverse osmosis system to be re-permeated.

The backwash module 400 may be provided as a pressure vessel or apressure tank. Some of the raw water fed by the raw water pump 200 isfed to the backwash module 400. For this purpose, a separate transfertube is connected to a back end of the raw water pump 200.

The backwash water for backwash uses some of the permeate waterpermeated by the filtration module 300 and some of the permeate water isfed to the pressure vessel or the pressure tank of the backwash module400. For this purpose, the separate transfer tube is branched from thepermeate water outlet and thus is connected to the backwash module 400.

As the backwash water, the permeate water in the pressure vessel or thepressure tank is fed to the filtration module 300 by the pressureapplied into the pressure vessel or the pressure tank. The water usedfor backwash the filtration membrane of the filtration module 300 isdischarged to a separate dirtywash water tank. If the backwash iscompleted, the raw water within the backwash module is discharged andthe backwash module is again filled with some of the permeate water(refer to FIG. 2).

The operating principle of the backwash module 400 will be describedbelow in more detail.

The backwash module 400 is provided with two inlets and outlets, inwhich one inlet is introduced with the raw water and the other inlet isintroduced with the permeate water, and the backwash module 400 isfurther provided with a plurality of valves 500. Further, the raw wateris discharged to one outlet and the permeate water for backwash isdischarged to the other outlet. The inlet into which the raw water isintroduced is provided with a first valve 510 and a flow meter 512 andthe outlet to which the raw water is discharged is provided with asecond valve 530. Further, the outlet to which the permeate water isdischarged is provided with a third valve 550 and the inlet into whichthe permeate water is introduced is provided with a fourth valve 570.The first valve 510 may be provided as a flow control valve and thesecond to fourth valves 530, 550, and 570 may be provided as the on/offvalve.

When some of the permeate water purified by passing through thefiltration module 300 is introduced into the pressure vessel or thepressure tank of the backwash module 400, the first valve 510 and thethird valve 550 is closed and the second valve 530 and the fourth valve570 are open. Therefore, the inside of the pressure vessel or thepressure tank is filled with the permeate water.

Upon the backwash, the second valve 530 and the fourth valve 570 areclosed and the first valve 510 and the third valve 550 are open, andthus the permeate water in the pressure vessel or the pressure tank isdischarged through the third valve 550 by the introduction pressure ofthe raw water.

Generally, the operating pressure of the filtration module 300 is equalto or more than 3 bars but the backwash pressure is enough to be equalto or less than 3 bars. Therefore, even though a separate pump forfeeding the backwash water is not provided, the backwash water may befed to the filtration module 300 only by the feed pressure of the rawwater.

Hereinafter, various forms of the backwash module 400 will be described.

FIG. 2 is a schematic diagram of a first embodiment of a backwash moduleaccording to the water purifying system of FIG. 1 and FIG. 3 is aschematic diagram of a second embodiment of the backwash moduleaccording to the water purifying system of FIG. 1.

As illustrated in FIGS. 2 and 3, backwash modules 400 a and 400 b may bea tube type pressure vessel.

The backwash module 400 a may be a horizontal type to an installationsurface as illustrated in FIG. 2 but the pressure vessel 400 b may be avertical type to the installation surface as illustrated in FIG. 3.

The inside of the pressure vessel of FIG. 3 may be provided with apiston 402 and the feed direction of the raw water and the dischargedirection of the backwash water may be disposed on a straight line.

The pressure vessel of FIG. 3 is not illustrated in the drawing, butlike the horizontal type, the inside of the pressure vessel is providedwith the piston. In this case, the discharge direction of the backwashwater corresponds to an arrow direction.

FIGS. 4 and 5 are schematic diagrams of a fourth embodiment of thebackwash module according to the water purifying system of FIG. 1.

As illustrated in FIGS. 4 and 5, a backwash module 400 c according tothe present invention may be configured to include the pressure tank 410and a diaphragm 412 installed in the pressure tank 410.

As illustrated in FIG. 4, the diaphragm 412 moves a lower portion of thepressure tank 410 by the feed pressure of the raw water fed from anupper portion of the pressure tank 410 and discharges the previouslyfilled backwash water to the lower portion of the pressure tank 410. Asillustrated in FIG. 5, the pressure of the permeate water after thebackwash introduced into the lower portion of the pressure tank 410moves the diaphragm 412 to the upper portion of the pressure tank 410discharges the raw water filled in the pressure tank 410 to the upperportion of the pressure tank 410.

The upper and lower portions of the pressure tank 410 are provided witha pair of plates 414 which is formed corresponding to a movement limitposition of the diaphragm 412. Further, the plate 414 is provided with aplurality of through holes and therefore does not hinder the movement ofthe raw water or the backwash water.

FIGS. 6 and 7 are schematic diagrams of a fourth embodiment of thebackwash module according to the water purifying system of FIG. 1.

As illustrated in FIGS. 6 and 7, a backwash module 400 d according tothe present invention may be configured to include the pressure tank 420and a balloon-like diaphragm 422 installed in the pressure tank 420.

As illustrated in FIG. 6, the pressure of the raw water applied from theupper portion of the pressure tank 420 presses the diaphragm 422 fromthe outside and the backwash water in the diaphragm 422 is discharged tothe lower portion of the pressure tank 420 while the diaphragm 422 ispressurized by the pressure of the raw water. As illustrated in FIG. 7,the diaphragm 422 is inflated by the pressure of the permeate waterafter the backwash that is introduced from the lower portion of thepressure tank 420 into the diaphragm 422 to push the raw water filled inthe outside of the diaphragm 422 to the upper portion of the pressuretank 420, thereby discharging the raw water.

As such, if some of the permeate water permeated by the filtrationmodule 300 is used as the backwash water, it is preferable to design andoperate a system to produce more permeate water as much as the amount ofpermeate water required for the backwash.

When the permeate water is not stored in the permeate water storage tankand is directly connected to a feed water tube of the reverse osmosissystem, the feed water fed to the reverse osmosis system is reduced asmuch as the amount of backwash water used for the backwash. To solve theproblem, the reduction in flux of the feed water to the reverse osmosissystem may be supplemented by increasing the processing capacity of theraw water pump 200 and increasing the flux of the raw water.

A flow of fluid by processed state in the water purifying systemaccording to the present invention having the foregoing configurationwill be described below (refer to FIG. 1).

First, if the raw water is fed from the raw water 100 to the raw waterpump 200, the raw water is fed to each of the filtration modules 300through the plurality of valves. In this case, the flow direction of theraw water and the permeate water passing through the filtration module300 is a direction toward the separate permeate water storage tank andthe valves are open toward the corresponding direction.

At the backwash time set in the system, first, some of the permeatewater is fed to the backwash module 400 through the transfer tubebranched from the transfer tube, connected to the permeate water storagetank. In this case, a first valve 510 and a third valve 550 are in aclosed state and a second valve 530 and a fourth valve 570 are in anopen state. The fourth valve 570 is open toward the backwash module 400.Next, some of the raw water is fed from the backwash module 400 throughthe transfer tube branched from the back end of the raw water pump 200and the first valve 510 and the third valve 550 are in the open stateand the second valve 530 and the fourth valve 570 are in the closedstate.

The flux of raw water fed to the first valve 510 is detected by the flowmeter 512. The first valve 510 adjusts a flux depending on the detectedresult and thus the raw water is fed to the backwash module 400. Forthis purpose, the first valve 510 is preferably provided as the flowcontrol valve. The backwash flux may be preset upon the design of thesystem. As the backwash water, the permeate water in the backwash module400 is fed to the filtration module 300 by the feed pressure of the rawwater. A front end of the third valve 500 for discharging the backwashwater to the filtration module 300 may also be provided with the flowmeter, if necessary. The operation of the filtration module 300 stopswhen the backwash is performed, and the valves for feeding the raw waterare closed and only the valves for feeding the backwash water are open.The washing water including the foreign materials after the backwash isdischarged to the separate dirty water tank. After the backwash iscompleted, all the valves for feeding the backwash water are closed andthe valves for feeding the raw water for purification are open.

After the backwash, the backwash module 400 is again filled with thepermeate water. For this purpose, the first valve 510 and the thirdvalve 550 are closed and the second valve 530 and the fourth valve 570are open.

As described above, various types of backwash modules may be providedand the backwash water may be fed only by the feed pressure of the rawwater without the separate backwash water feeding pump, thereby reducingthe energy consumption.

According to the water purifying system and the backwash module controlmethod thereof in accordance with the embodiment of the presentinvention, it is possible to save the capital expenditure (CAPEX) uponthe construction of the backwash system by performing the backwash ofthe filter module using the pressure of the produced water for membranefiltration without the backwash pump. Further, it is possible to reducethe energy consumption by removing the backwash pump.

The various exemplary embodiments of the present invention, which isdescribed as above and shown in the drawings, should not be interpretedas limiting the technical spirit of the present invention. The scope ofthe present invention is limited only by matters set forth in the claimsand those skilled in the art can modify and change the technicalsubjects of the present invention in various forms. Therefore, as longas these improvements and changes are apparent to those skilled in theart, they are included in the protective scope of the present invention.

What is claimed is:
 1. A method of controlling a backwash moduleconfigured to perform a backwash by feeding backwash water to a rawwater filter, the backwash module including a first inlet configured toreceive raw water from a tank storing the raw water, a second inletconfigured to receive a portion of permeate water permeated by the rawwater filter, a first outlet through which the received raw water isdischarged, and a second outlet through which the backwash water isdischarged, the method comprising: using the received raw water to applypressure to the portion of permeate water such that the backwash modulefeeds the portion of permeate water to the raw water filter as thebackwash water, and using the received portion of the permeate water toapply pressure to the received raw water such that the backwash modulefeeds the raw water back to the tank.
 2. The method of claim 1, furthercomprising: opening second and fourth valves (530, 570) respectivelyconnected to the first outlet and the second inlet in order to feed theportion of the permeate water to the backwash module; and opening firstand third valves (510, 550) respectively connected to the first inletand the second outlet in order to perform the backwash.
 3. The method ofclaim 2, wherein the first and third valves (510, 550) are closed whenfeeding the portion of the permeate water to the backwash module, andwherein the second and fourth valves (530, 570) are closed whenperforming the backwash.
 4. The method of claim 1, further comprising:detecting a flux of the raw water received from the tank; andcontrolling the flux of the raw water at the first inlet depending onthe detecting.
 5. The method of claim 4, wherein the flux of the rawwater is controlled based on a preset backwash flux.
 6. The method ofclaim 1, further comprising stopping an operation of the raw waterfilter when the backwash is performed by stopping a flow of the rawwater to the raw water filter during the backwash.
 7. The method ofclaim 1, further comprising controlling the pressure applied to theportion of permeate water by pumping the raw water received from thetank to the backwash module.
 8. The method of claim 7, furthercomprising: directly applying the permeate water from the raw waterfilter to a reverse osmosis system such that water fed to the reverseosmosis system is reduced by as much as an amount of the backwash waterused for the backwash; and compensating for the reduction in flux of thefeed water to the reverse osmosis system by increasing a flux of the rawwater pumped to the backwash module.
 9. The method of claim 1, furthercomprising: discharging the backwash water to a dirty water tank afterthe backwash of the raw water filter such that water fed to the backwashmodule is reduced by as much as an amount of the backwash waterdischarged to the dirty water tank.
 10. The method of claim 1, furthercomprising: compensating for the reduction in flux of the feed water tothe backwash module by increasing an amount of permeate water suppliedto the backwash module as a required amount of the backwash waterincreases.
 11. A backwash module configured to perform a backwash byfeeding backwash water to a raw water filter, the backwash modulecomprising: a first inlet configured to receive raw water from a tankstoring the raw water; a second inlet configured to receive a portion ofpermeate water permeated by the raw water filter; a first outlet influid communication with the raw water tank and through which thereceived raw water is discharged to the raw water tank; and a secondoutlet through which the backwash water is discharged, wherein thebackwash module includes a pressurized volume formed as one of apressure vessel and a pressure tank, and wherein the pressurized volumeis compartmentalized by first and second porous plates to include: afirst compartment communicating with the first inlet and the firstoutlet; a second compartment communicating with the second inlet and thesecond outlet; and a common compartment configured to receive the rawwater through the first porous plate and to receive the backwash waterthrough the second porous plate.
 12. The backwash module of claim 11,further comprising: a first valve (510) to control the raw waterreceived at the first inlet; a second valve (530) to control the rawwater discharged at the first outlet; a third valve (550) to control thebackwash water discharged at the second outlet; and a fourth valve (570)to control the permeate water fed to the second inlet.
 13. The backwashmodule of claim 11, wherein the pressurized volume consists of aplurality of pressurized volumes arranged according to one of a verticalpattern and a horizontal pattern, each of the plurality of pressurizedvolumes including a movable member configured to move lengthwise withinthe pressurized volume in correspondence with a cycle of a presetbackwash time.
 14. The backwash module of claim 11, further comprising:a movable member configured to move between the first and second porousplates, wherein the movable member travels toward the first porous platewhen the portion of permeate water is received at the second inlet, andtravels toward the second porous plate when the raw water is received atthe first inlet.
 15. The backwash module of claim 14, furthercomprising: the movable member configured to move between the first andsecond porous plates, wherein the movable member travels toward thefirst porous plate when the raw water is discharged from the firstoutlet, and travels toward the second porous plate when the backwashwater is discharged from the second outlet.
 16. The backwash module ofclaim 15, wherein the movable member is one of a piston and a diaphragm.17. A backwash module configured to perform a backwash by feedingbackwash water to a raw water filter, the backwash module comprising: afirst inlet configured to receive raw water from a tank storing the rawwater; a second inlet configured to receive a portion of permeate waterpermeated by the raw water filter; a first outlet through which thereceived raw water is discharged; a second outlet through which thebackwash water is discharged; and first and second porous platesconfigured to compartmentalize a pressurized volume in the backwashmodule, the pressurized volume including a first compartmentcommunicating with the first inlet and the first outlet, a secondcompartment communicating with the second inlet and the second outlet,and a common compartment configured to receive the raw water through thefirst porous plate and to receive the backwash water through the secondporous plate, wherein the first outlet is in fluid communication withthe raw water tank and the raw water from the first compartment is fedback to the raw water tank via the first outlet.
 18. The backwash moduleof claim 17, further comprising: a second valve to control the raw waterdischarged at the first outlet; and a fourth valve to control thepermeate water fed to the second inlet, wherein the second and fourthvalves (530, 570) are opened in order to feed the portion of thepermeate water to the backwash module and are closed when performing thebackwash.
 19. The backwash module of claim 17, further comprising: afirst valve to control the raw water received at the first inlet; and athird valve to control the backwash water discharged at the secondoutlet; and wherein the first and third valves (510, 550) are opened inorder to perform the backwash and are closed when feeding the portion ofthe permeate water to the backwash module.